Left-sided appendicitis revealing a common mesentery: A Case Report

Intestinal malrotation is a congenital rotational anomaly that results of abnormal rotation of the gut, said to occur in 1 in 6000 live births. Common mesentery predisposes to volvulus of the midgut and internal hernias due to the left position of the cecum and appendix. The association of this anomaly with acute left appendicitis is rarely reported in the literature. Occurrence of acute appendicitis on common mesentery is a source of diagnosis difficulties, which may lead to a surgical management delay. We report a case of a 10-year-old boy, admitted for a left-sided iliac pain whose radiological investigations confirmed a left acute appendicitis associated with complete common mesentery. The child underwent laparoscopic surgery with simple post-operative follow-up.


Introduction
Intestinal malrotation is a rare congenital abnormality estimated to occur in one of 6000 live births [1] . Historically, intestinal malrotation was mainly considered a pediatric disease, and it is rarely diagnosed after the age of 1 year. However, this perception is changing with increased documented presentations above that age [2 ,3] .
Acute appendicitis in this condition has a high risk of missed and delayed diagnosis; therefore, it poses a significant diagnostic challenge [4] . Majority of cases with left sided appendicitis have an associated midgut malrotation, situs inversus totalis or an abnormal position of a long appendix. Due to the ambiguity of symptoms, diagnosis is often difficult and thus increases morbidity and mortality.
Our case focuses on acute appendicitis of left localization with complete common mesentery, which first line of investi-

Case presentation
A 10-year-old boy without pathological medical or surgical history, admitted to the pediatric emergency department for a 3 days' acute abdominal pain. It was not improved by symptomatic treatment with paracetamol.
Clinical examination revealed a soft abdomen with a localized febrile tenderness on the left iliac fossa and hypogastrium. Hemodynamic and respiratory values were normal, they revealed a 129/75 mmHg of blood pressure, and a 95/min heart rate.
Abdominal ultrasound does not show appendix on the right iliac fossa; however, it identified a hyperechoic structure generating a posterior acoustic shadowing within dilated tubular structure in the left iliac fossa. There was no intraabdominal free fluid and the liver, spleen and both kidneys were normal.
Contrast-enhanced abdominal CT scan was performed, revealing a severely inflamed appendix that was significantly dilated to 14 mm in the left iliac fossa with 12 mm appendicolith ( Fig. 1 ). CT scan also demonstrated typical imaging findings of intestinal malrotation including: abnormal position of small intestine located in the right and large bowel in the left, reversal of the normal relationship between the superior mesenteric artery and superior mesenteric vein, and also the absence of a D3 segment that does not cross the median line and continues toward a vertical trajectory.
In this case, we concluded to intestinal malrotation with acute left-sided appendicitis.
An emergency laparoscopic procedure was performed ( Fig. 2 ), and revealed inflamed appendicitis with a stercolith localized in the left iliac fossa which confirmed the initial presumption. There was no associated abscess or free intraperitoneal fluid.
Appendicectomy was done and follow-up was without complications: the child resumed normal transit, the wound was clean and the DELBET blades were removed within 24 hours.
Postoperative control CT scan showing the migration of stercolith, currently located at the level of the cecal fundus ( Fig. 3 ).

Discussion
Several pathological conditions can cause left lower abdominal pain. Digestive causes are the most common especially acute diverticulitis, ulcerative colitis, Crohn's disease and ir-  ritable bowel syndrome. Other pathologies may be also considered such as urinary causes, ovarian disease, fallopian inflammation or even a parietal origin [4] . Acute appendicitis is barely considered in the differential diagnosis of left lower abdominal pain.
Acute left iliac pain caused by appendicitis still an ambiguous and challenging diagnosis, and thus, diagnosis is frequently delayed leading to more severe complications.
It is important to know that excessively long right appendicitis that crosses the midline can always mimic a true left appendicitis found in cases of situs inversus or midgut malrotation [5 ,1] .
Midgut malrotation is used to describe a spectrum of congenital positional anomalies of the digestive tract that's results from incomplete rotation of the primitive midgut around the axis of superior mesenteric artery during embryogenesis [6] .
Approximately, 50% of cases present in the first week of life while 60% are diagnosed in the first month of life due to the severe complications of midgut volvulus [6] . Other conditions may be diagnosed in childhood or adulthood either due to primitive complications (midgut volvulus / internal hernias) or even incidentally during the investigation of acute or chronic pathologies involving abdominal pain such as in our case [7 ,8] .
Ultrasonographic assessment of common mesentery is proposed as advantageous for children, because aside from its high accuracy, it lacks the radiation effects in comparison with other imaging studies.
Inversion of superior mesenteric vessels is considered to be the key diagnosis of the disease. In a study of 23 patients, Zhou et al. reported sensitivity, specificity, and accuracy of ultrasonography for determining malrotation at 100%, 97.8%, and 98.6%, respectively [9] .
CT scan and MRI may confirm SMV and SMA inversion; it can identify a right SMA and a left SMV. This abnormal deviation was originally described by Nichols and Li.
In addition, they may demonstrate the abnormal anatomical arrangements of retro-mesenteric D3 segment of the duodenum which does not cross the spine.
In our case, ultrasound could not confirm the diagnosis, and thus an enhanced abdominal CT scan was carried out, revealing typical features of complete intestinal malrotation.
Situs inversus is the major differential diagnosis of acute appendicitis with common mesentery, it may be complete when there is an inverted position of chest and abdominal organs (situs inversus totalis-SIT) or partial when only one of those cavities is affected.
Some authors such as Collins D reported that the incidence of acute appendicitis associated with SIT after studying 71000 human appendix specimens is 0.016% [5] . In more recent study of 95 cases of LSA published in literature, 69.4% had SIT while 24.2% had midgut malrotation [10] .

Conclusion
LSA is a rare condition that is not usually encountered in the differential diagnosis of left abdominal pain in children. The